ISIS have declared a caliphate spanning parts of northern Iraq and Syria.

Reuters

The leader of the Al Qaeda offshoot that has taken control of parts of Iraq and Syria has urged Muslims around the world to fight to avenge wrongs committed against their religion.

Abu Bakr al-Baghdadi, the head of the Islamic State - previously known as the Islamic State in Iraq and Syria (ISIS) - issued the call to jihad, or holy war, in an audio message posted online, lasting nearly 20 minutes.

It was his first purported message since the group proclaimed a 'caliphate' on the territory it has captured.

Baghdadi named a string of countries, from Central African Republic to Myanmar (Burma), where he said violations were being committed against Muslims.

"Your brothers, on every piece of this earth, are waiting for you to rescue them," he said.

"By Allah, we will take revenge, by Allah we will take revenge, even if after a while," he said in the message that came on the third day of the Muslim holy month of Ramadan.

Fighters should "embrace the chance and champion Allah's religion through jihad", Baghdadi said.

He called on Muslims to immigrate to the self-styled Islamic State, saying it was their duty.

On Sunday, ISIS claimed universal authority throughout the Muslim world, declaring Baghdadi its caliph - a mediaeval title last widely recognised in the Ottoman sultan deposed 90 years ago, after World War I.

The move followed a three-week drive for territory by ISIS militants and their allies among Iraqi's Sunni Muslim minority.

The caliphate aims to erase colonial-era borders and defy the US and Iranian-backed government of Shiite prime minister Nouri al-Maliki in Baghdad.

It also poses a direct challenge to the global leadership of Al Qaeda, which has disowned ISIS, and to conservative Gulf Arab Sunni rulers, who already view the group as a security threat.

First parliament session fails to name prime minister

Shiites failed to name a prime minister to replace Mr Maliki at the first meeting of a new parliament session, dashing hopes a unity government would be swiftly built to save Iraq from collapse.

The United States, United Nations, Iran and Iraq's own Shiite clergy have pushed hard for politicians to come up with an inclusive government to hold the fragmenting country together as Sunni insurgents bear down on Baghdad.

Anger among the three main ethnic and sectarian groups soon flared when a Kurdish lawmaker accused the government of withholding salaries for the Kurds' autonomous region. Kadhim al-Sayadi, a lawmaker shouted back that Kurds were taking down Iraqi flags.

What is a caliphate?

A caliphate is essentially an Islamic state which resides over the entire Muslim faith.

Its head of state is called the caliph, who will interpret and implement the will of Allah on Earth.

Sunnis and Shiites differ in their beliefs on how a caliph should be selected. Sunnis believe they are elected by the people. Shiites believe a caliph should be an imam, a religious teacher, descended from the family of the prophet Muhammad, and who is chosen by Allah.

There are four recognised caliphates, with more than 100 caliphs serving since the death of the prophet Muhammad in 632 AD.

Caliphs from the first caliphate, the Rashidun Caliphate, were elected with subsequent caliphs appointed though succession or takeovers. In theory, the declarations of a caliphate are binding for all Muslims; however, their authority must be recognised for this to happen.

Source: Keysar Trad, spokesman for the Australian Federation of Islamic Councils.

The session collapsed when Sunnis and Kurds refused to return from a recess to the parliamentary chamber after Shiites failed to name a prime minister.

Parliament is not likely to meet again for at least a week, leaving Iraq in political limbo and Mr Maliki clinging to power as a caretaker, rejected by Sunnis and Kurds.

Under a governing system put in place after the removal of Saddam Hussein, the prime minister has always been a member of the Shiite majority, the speaker of parliament a Sunni and the largely ceremonial president a Kurd.

The Shiite bloc known as the National Alliance, in which Mr Maliki's State of Law coalition is the biggest group, has met repeatedly in recent days but has so far been unable either to endorse Mr Maliki for a third term or to name an alternative.

Sunni parties said they would not put forward their candidate for speaker until the Shiites pick a premier. The Kurds have also yet to nominate a president.

Osama al-Nujaifi, a leading Sunni politician, former speaker and strong foe of Mr Maliki, warned that "without a political solution, the sound of weapons will be loud, and the country will enter a black tunnel".

Fighting continues with 2,400 killed in June

The dramatic advance by ISIS, which has dominated swathes of territory in an arc from Aleppo in Syria to near the western edge of Baghdad, has stunned Iraq and the West. The group and allied militants seized border posts, oilfields and northern Iraq's main northern city Mosul in a lightning offensive in June.

Fighting has raged in recent days near former dictator Saddam Hussein's home city, Tikrit, north of Baghdad. ISIS also controls suburbs just west of the capital and clashes have erupted to the south, leaving the city of 7 million confronting threats from three sides.

Kurds have taken advantage of the advance to seize territory, including the city of Kirkuk, which they see as their historic capital and which sits above huge oil deposits.

The United Nations said on Tuesday more than 2,400 Iraqis had been killed in June alone, making the month by far the deadliest since the height of sectarian warfare during the US "surge" offensive in 2007.

In a reminder of that conflict, mortars fell near a Shiite holy shrine in Samarra which was bombed in 2006, unleashing the sectarian bloodshed that killed tens of thousands over the next two years. Samarra, north of Baghdad, is now held by Baghdad's troops with ISIS in the surrounding countryside.

Your brothers, on every piece of this earth, are waiting for you to rescue them. By Allah, we will take revenge, by Allah we will take revenge, even if after a while.

ISIS leader Abu Bakr al-Baghdadi

Violence also struck the capital, where police found two bodies with their hands tied behind their back and bullet wounds in the head and chest in the mainly Shiite neighbourhood of Shula, police and medical sources said.

A bomb went off in Baghdad's western Jihad district, killing two passersby and wounding six more, police and medics said.

The insurgents' advance has triggered pledges of support for Baghdad from both Washington and Tehran.

Iran's deputy foreign minister said his country had not received any request for weapons from Baghdad but was ready to supply them if asked.

Iraq also flew Russian-made Sukhoi Su-25 jets delivered on Saturday for the first time, state television reported, although there was no independent confirmation.

Saudi Arabia pledged $500 million in humanitarian aid for Iraqis to be disbursed through UN agencies, a Saudi Press Agency statement said.

Washington has so far pledged 300 mainly special forces advisers and said on Monday it was sending a further 300 troops to help secure the embassy and Baghdad airport.

Maliki's government has managed to stop the militants short of the capital but has been unable to take back cities its forces abandoned.